Cryptology ePrint Archive: Report 2016/590

Mitigating SAT Attack on Logic Locking

Yang Xie; Ankur Srivastava

Abstract: Logic locking is a technique that has been proposed to protect outsourced IC designs from piracy and counterfeiting by untrusted foundries. It can hide the functionality of an IC by inserting key-controlled logic gates into the original design. The locked IC preserves the correct functionality only when a correct key is provided. Recently, the security of logic locking is threatened by a new type of attack called satisfiability checking (SAT) based attack, which can decipher the correct key of most logic locking techniques within a few hours [11] even for reasonably large number of keys. This type of attack iteratively solves SAT formulas which progressively eliminate the incorrect keys till the circuit unlocked. In this paper, we present a specially designed circuit block (referred to as Anti-SAT block) to thwart the SAT attack. We show that the number of SAT attack iterations to reveal the correct key in a circuit comprising an Anti-SAT block is an exponential function of the key-size thereby making the SAT attack computationally infeasible. This is a substantial result because a) we illustrate how to construct the functionality of the Anti- SAT block and b) using a mathematically rigorous approach to prove that if chosen correctly, the Anti-SAT block makes SAT attack computationally infeasible (exponential in key-size). Moreover, through our experiments, we illustrate the effectiveness of our approach to securing modern chips fabricated in untrusted foundries.

Category / Keywords: Logic Locking; SAT Attack; Hardware IP Protection

Original Publication (in the same form): IACR-CHES-2016

Date: received 5 Jun 2016

Contact author: yangxie at umd edu, ankurs@umd edu

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Version: 20160606:150522 (All versions of this report)

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